Digital image based object detection, especially with respect to traffic sign recognition (TSR), has seen increased attention over the past few years. For example, object detection systems are currently being implemented in advanced driver assistance systems (ADAS). Conventional object detection methods usually involve two stages. First, in the detection stage, image regions that contain candidates of target objects are detected or localized. Then, in the recognition stage, such regions are further analyzed to recognize the specific content. However, these conventional object detection systems and methods generally require a large amount of computing resources, have slow detection speeds, and can be inaccurate.